A controversial Chinese-developed gene editing tool has come under academic fire for a second time in less than a week with researchers from 18 laboratories in China and overseas failing to replicate the initial findings.

A study published in the journal Protein & Cell on Tuesday challenged the NgAgo technology developed by biologist Han Chunyu and his team saying it was ineffective in altering the genes of fish, mice and humans.

Another study in the journal Cell Research last Friday found Han’s method could not be used to edit the genes of zebra fish.

Han’s team claimed in May that a protein in the bacteria NgAgo could be used as “scissors” to edit the DNA sequence of animals, including humans.

The new technology was touted as better in some ways than CRISPR/Cas9, the most popular genome editing tool in use today, with some advocates saying it was Noble Prize-worthy research.

Once Han published his findings in the journal Nature Biotechnology, the provincial and central authorities moved swiftly to approve more than 200 million yuan (HK$226) in funding for his small, cash-strapped laboratory at Hebei University of Science and Technology.

In the Protein & Cell study, the researchers performed Han’s experiments independently at various laboratories, but observed no NgAgo-induced insertion or deletion in DNA sequences. They tried an updated method released by Han, but still in vain.

The laboratories were at prominent life science research institutes, including the Chinese Academy of Sciences, the National Human Genome Research Institute in the United States, Peking University, Johns Hopkins University, Sun Yat-sen University, Harbin Institute of Technology, Shanghai Jiao Tong University, and the University of California Los Angeles.

Han did not answer phone calls requesting comment.

Han said in previous interviews with mainland media that other scientists had failed to replicate his team’s results because their samples were contaminated, but the latest study cast doubt on this claim.

“It seems unlikely that independent laboratories would all have their cells contaminated, resulting in consistently negative results for DNA editing activity,” the authors said in the paper.

They added they had made sure their cells were free of contamination by first testing them before performing experiments.

Han also said the NgAgo technology required expert handling but “neither the originally published protocol nor the newly released information … involves any steps that seem to require ‘superb experimental skills’,” the authors said.

“To gain insights into NgAgo’s utility, some of us have even sent visiting researchers to Han’s laboratory, but they were not allowed to perform genome editing experiments involving mammalian cells when they were there. Consequently, none of them returned with any information confirming Han’s data.

“We therefore urge the authors of the original paper to clarify the uncertainty surrounding NgAgo and provide all the necessary details for replicating the initial, very important results,” the report said.

This article appeared in the South China Morning Post print edition as: